For many years lead-acid batteries, and particularly lead-acid automotive batteries have incorporated battery grids cast of lead-antimony grid alloys. These lead-antimony alloys exhibit suitable hardness and resistance to corrosion, however have the undesirable side effect of encouraging "local action", sulphation and gassing that is, electrolysis of the sulfuric acid solution during overcharging.
More recently with the development of what has been termed "maintenance free" batteries -- batteries which are not intended to have water added to them, or to which water is to be in-frequently added -- practitioners in the art have begun to look for other materials which exhibit suitable strength, castability, hardness, and corrossion resistance, while eliminating the gassing and other problems heretofore exhibited by high antimony grid alloys.
For many years it has been known to utilize either strontium or calcium, with or without tin, in lead alloys used to form the grids of storage batteries.
In U.S. Pat No. 2,040,078 entitled, "Lead Alloy", dated May 12, 1936 strontium is disclosed as imparting a desirable degree of hardness to lead, while overcoming certain disadvantages previously associated with lead-antimony alloys. For instance, 0.08% strontium added to pure lead is disclosed as providing an alloy which, after quenching from 300.degree. C. and aging for 3 weeks at 100.degree. C., has a Brinell hardness from 7 to 9, which is a desirable hardness for storage battery grids. Alternatively, U.S. Pat. No. 2,040,078 discloses the use of strontium in combination with tellurium.
Also of interest to the present application is U.S. Pat. No. 2,013,487 entitled, "Lead Alloy", dated Sept. 3, 1935 wherein it is disclosed that good results were obtained with alloys containing from 0.2% to 1.5% of one of the elements chosen from the group of barium, strontium, and calcium; tin from 0.2% to 2.0%; and with the remainder being lead. In particular, U.S. Pat. No. 2,013,487 additionally discloses that any two or all three of the metals barium, calcium and strontium may be used in the same alloy "providing the total percentage thereof lies between 0.2% and 1.5%, the quantity of tin being as above mentioned". (all percentages being taken by weight).